UREA • I27 and froth up. When it fuses quietly, the dark coloured liquid mass is poured on to an iron pl.tie and allowed to cool. It solidifies and is powdered and separated from the solid cake of metallic lead. 200 c.c. of cold water are poured on to the crude cyanate and, after standing- an hour, filtered through a fluted filter and washed with a little cold water. A concentrated solution of 25 grains of ammonium sulphate is immediately added to the filtrate, which is evaporated to dryncss on the water-bath, the mass being stirred occa- sionally to prevent the formation of a surface crust. The cooled residue is powdered and the urea extracted with alcohol by boiling on the water-bath, using a reilux condenser and adding successively small quantities of spirit until the extract leaves only a small residue on evaporation on a watch-glass. The greater part of the alcohol is distilled off on the water- bath, and the residue poured out into a beaker to crystallise. Yield about 15 grams. 1. 4KCN + Pb,,04 = 4CONK + 3Pb 2. (NH4)3SO,i + 2CONK - 2CON.NH4 + K>SO4 3. CO N. N H4 = C0( N H2)sj Properties. — Colourless prisms ; in. p. 132°; very soluble in water ; soluble in hot alcohol. Reactions. — r. Add to a strong solution of urea in water a drop of concentrated nitric acid, and to another portion a concentrated solution of oxalic acid ; the crystalline nitrate CO(NH3)2HNO., and oxalate (.CO(NH2)2)2CaHaO,, are deposited. 2. Melt a few crystals of urea over a small flame and heat gently for a minute, so that bubbles of gas arc slowly evolved. Cool and add a few drops of water, then a drop of copper sul- phate solution, and finally a few drops of caustic soda. A violet or pink coloration is produced, depending upon the quantity of biurct formed. 2CO(NHs)a = N 3. Add a few drops of sodium hypochlorite, or hypobromitc, to a solution of urea in water. Nitrogen is given off, CO(NH2)2 + 3NaOCl -"- N2-f-2lIaO H- 3NaCl + CO, (which dissolves in the alkaline solution).